Recently, semiconductor devices such as a LSI or the like have been required to have higher density in order to meet requirements for reducing the mounting space or for improving the processing rate. As an example of a technology that achieves the high density, there has been known a multilayer wiring technology of manufacturing a multilayer substrate, such as a three-dimensional LSI or the like, by stacking multiple wiring substrates.
According to the multilayer wiring technology, a TSV (Through Silicon Via), which penetrates the wiring substrates and in which a conductive material such as copper (Cu) is buried, is typically formed in the wiring substrate in order to obtain electrical connection between the wiring substrates. As an example of a technology for forming the TSV in which a conductive material is buried, there has been known an electroless plating method.
In case of forming a metal film by electroless plating, it is required to improve adhesivity between a base and the metal layer. For the purpose, conventionally, a self-assembled monolayer (SAM) is formed on the base by using a coupling agent such as a silane coupling agent or a titanium coupling agent, and a catalytic metal such as palladium particles is provided on the base with the self-assembled monolayer therebetween (see, for example, Patent Document 1).
In general, since a main component of the titanium coupling agent is TiOx, a performance of adsorption of metal catalytic particles is superior. Thus, by using the titanium coupling agent, adhesivity of the metal film can be improved, as compared to the case of using the silane coupling agent. Since, however, the titanium coupling agent cannot be adsorbed onto the substrate by a vacuum deposition process, it is very difficult to attach the titanium coupling agent in a deep hole such as a TSV having a high aspect ratio, or it takes a very long time to complete the process.
Meanwhile, since the silane coupling agent can be adsorbed onto the substrate through the vacuum deposition process, the silane coupling agent having high coverage can be attached even on an inner surface of a recess such as a TSV having a high aspect ratio. Since, however, the silane coupling agent has low adhesivity, a film formed at an outside of the recess may be separated by a membrane stress generated during a copper electroplating or by CMP (Chemical Mechanical Polishing).
Patent Document 1: Japanese Patent Laid-open Publication No. 2002-302773